Notice given on home loan, but the bank refusing to honour it.

I'm in the process of switching my homeloan to FNB. I've given Standard Bank notice of this plan on the mobile app in March. This is to avoid paying penalty interest. I've now contacted them to give me the date I gave notice on email so I can plan my transfer accordingly to avoid paying penalty interest. Now they gave me feedback to say there is no notice loaded on my home loan. Please contact me as to how this is possible. I refuse to pay penalty interest since i did give the required notice. Not my problem if the app is not carrying through the information.